Sealing fitting with expanding material

ABSTRACT

A fitting for connecting conduit. The fitting includes a plurality of electrical conductors running through the fitting and a sealing compound that has been expanded within the fitting to separate the electrical conductors from each other and sides of the fitting. In a further embodiment, the fitting includes a plurality of conductors running through the fitting and a sealing compound that has been expanded within the fitting to separate the conductors from each other and sides of the fitting. The fitting includes a first plug that is secured within a first opening in the fitting such that the first plug is inserted into the first opening after the sealing compound is added to the fitting through the first opening.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.10/391,250, filed on Mar. 18, 2003, now U.S. Pat. No. 7,341,255 which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to sealing conduits, and in particular toan expanding conduit sealer.

BACKGROUND OF THE INVENTION

Electrical conduit is used to mechanically protect electricalconductors. The U.S. National Electrical Code and Canadian ElectricalCode require that explosion-proof enclosures housing arcing and sparkingdevices be sealed off to prevent propagation of flames or gases throughthe conduit system, and to minimize the explosion pressures. Such sealsminimize the effects of pressure piling by acting as a barrier to stopburning gases from traveling through the conduit to other parts of thesystem.

When sealing conduit fittings, past methods utilize a fiber materialthat is weaved around each electrical conductor in the conduit toseparate them. The fiber material is also packed in to form a dam ateach end of a horizontal fitting, and at the bottom of a verticalfitting. A Portland type cement is then mixed with water and poured inthrough a funnel, puddled with a stick to remove air bubbles and left tocure for at least 24 hours.

The past methods were fairly labor intensive and error prone. Errorsresulted when electrical conductors were not separated or fittings werenot filled completely full with sealing compound. Further labor includedobtaining clean water and mixing containers and the use of a stick toremove air bubbles.

SUMMARY OF THE INVENTION

An expanding compound is used to seal conduit fittings. The compound isinjected into the fitting, and expands to separate conductors within thefitting. In one embodiment, the compound expands to four times its size,and hardens within approximately one hour. In a further embodiment, thecompound is a two-part product that is mixed in a self containedapplicator and injected into the fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a horizontal mount sealing fittingillustrating use of a sealing compound.

FIG. 2 is a cross section of the sealing fitting of FIG. 1 with expandedsealing compound.

FIG. 3 is a cross section of a vertical mount sealing fittingillustrating use of a sealing compound.

FIG. 4 is a cross section of the sealing fitting of FIG. 2 with expandedsealing compound.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which is shown by way ofillustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and thatstructural, logical and electrical changes may be made without departingfrom the scope of the present invention. The following description is,therefore, not to be taken in a limited sense, and the scope of thepresent invention is defined by the appended claims.

FIG. 1 shows a horizontal fitting 110 for joining two horizontallydisposed conduits via mating sets of threads 115 and 120 at each end offitting 110. The length of the fitting is approximately the distancebetween the two sets of thread, and the width of the fitting isapproximately equal to the outside diameter of the fitting.

Multiple conductors 123 are disposed within the fitting. Two openings125 and 130 are provided in the fitting 110. Removable plugs are used toplug the openings. Opening 125 is shown without the plug installed, anda plug 135 is shown installed in opening 130. Opening 130 is larger thanopening 125 in one embodiment. An expanding sealing compound 133 isprovided in a liquid state inside the fitting 110. One of the plugs maybe removed to allow injection of the sealing compound. In this exampleembodiment, the sealing compound is injected through opening 125.

In one embodiment, the sealing compound 133 is a two-part mixture thatstarts to expand once the two parts are mixed. When expanded, it fillsthe fitting 110 as shown at 210 in FIG. 2. The expanding compound worksits way between conductors so that as it expands, the conductors areseparated from each other. In one embodiment, the expanding compoundexpands four times its size immediately after being mixed. It is desiredthat when the compound is expanded, none of the conductors are touchingeither themselves, or sides of the fitting 110, and the compound expandsto fill the fitting 110 over at least a portion of the length of thefitting 110 referred to as a sealing chamber 137 which extends betweenthe two ends of the fitting 110. In one embodiment, the sealing chamber137 extends approximately about and partly past the hub stops 140 and145 on each end of the fitting. In a further embodiment, the sealingcompound forms an explosion proof seal.

In one embodiment, the expanding compound is provided in a cartridgewith the two parts or materials separated by a barrier, such as a foilbarrier partway between a top and bottom of the cartridge. The cartridgeis squeezed to deform the foil barrier, and a mixing rod is coupled to aplunger in the cartridge. The plunger is then pushed to the bottom ofthe cartridge by the rod. The rod is then pushed and pulled between thetop and bottom of the cartridge for approximately 40 to 50 strokes,where a stroke is one complete in and out cycle. The cartridge isrotated while the rod is pushed and pulled to ensure that the plunger isswiping all material in the cartridge.

In one embodiment, mixing is done within 30 seconds of starting themixing process, as pressure builds up on the inside of the cartridge asthe material starts to expand. At the last stroke, the mixing rod ispushed all the way to the bottom of the cartridge. The rod is thenpulled out, while the cartridge is squeezed to hold the plunger at thebottom. A nozzle is then attached to the top of the cartridge where therod was removed, and then the rod is used at the bottom of the cartridgeto push the plunger. This causes mixed liquid material, the expandingcompound, to be injected through the nozzle. In one embodiment, thecartridge is marked with volumetric increments corresponding toone-ounce segments for measuring the amount of compound injected. Thesealing fitting plug is promptly replaced and tightened to prevent thesealing compound from expanding outside the fitting and/or gellingaround the threads in the fitting that mate with corresponding threadson the plugs.

The term “compound” in one embodiment comprises the use of two or morematerials that are mixed and start expanding. In further embodiments,the compound is a single material that may start expanding at acontrolled time, such as by exposure to air or other gases or byelectrical stimulation, heat, or any other controllable event.

Typical applications are for sealing fittings in the ½ inch to 6 inchtrade sizes. The temperature of the compound should be between 4° C. and29° C. The compound in one embodiment will expand approximately 4 timesits size following injection. The amount of compound for different sizefittings may be established empirically, but is approximately one fourthof the volume of the sealing chamber. Some hazardous areas that theseals may be used in include, but are not limited to Class I, Division 1& 2 Groups A, B, C, D and Class I, Zones 0, 1 & 2.

In one embodiment, the compound used is Chem-Cast 637 sealing foam c/oChem-Cast 637 isocyanate and Chem-Cast 637 Polyol. Isocyanate is a darkbrown liquid, insoluble in water with a boiling point of 392 degrees F.(200 degrees C.), a vapor density of 0.00016 (mm Hg) and a specificgravity of 1.2 g/ml. Polyol is a gray liquid, partially soluble in waterwith a specific gravity of 1.05 g/ml. When mixed together the resultantmaterial is gray in color. It has a rise time of 1.5-2.5 minutes and agel time of 4-5 minutes. When fully cured the foam density is 15-20lbs./ft³. The compression strength is >60 psi, porosity is >90% closedcell and has a water absorption of <1%. Chem-Cast 637 is a fireresistant two-partrigid, polyurethane foam. It expands to fill voidsinside of the sealing fitting and forms a dense, high strength foam. Ithas excellent adhesion to many surfaceswithout the use of primers.

FIG. 3 shows a vertical fitting 310 for connecting two verticallydisposed conduits via threads 315 and 320. Multiple conductors 323 aredisposed within the fitting. One or more openings 325 and 327 provideaccess to the inside of the fitting. Threaded plugs are used to plug theopenings. One plug 328 is shown installed in opening 327, which is alower opening. In one embodiment, opening 325 is a top opening thatprovides access to the inside of the fitting 315 to inject the liquidcompound. Opening 327 provides access to create a fiber dam 330 at abottom of the fitting, referred to as a hub. In one embodiment, thefiber is a mineral fiber, such as Chico X® sealing compound provided byCrouse-Hinds and it is packed using a hardwood stick of other tool thatwill not damage the conductors. Hub sizes range from ½ inch to 6 inches.

The fiber is first packed while the conductors are forced away from thehub opening and forced apart. The fiber is then packed between andaround conductors in the hub to form the dam 330. An area above the dam330 is referred to as a sealing chamber 340. The dam provides a means ofblocking the un-gelled expanding compound 342 from leaking out of thesealing chamber. Care should be taken to ensure no shreds of fiber areleft clinging to the side wall of the sealing chamber or to theconductors. Such shreds when imbedded in the sealing compound may formleakage channels. The completed dam should be even with an internalbushing 350, also referred to as a conduit stop. For the horizontalfitting, no dams are required, but may be used if desired.

FIG. 4 shows vertical fitting 310 with a plug 410 installed quicklyafter the compound is inserted, and it shows the compound in a fullyexpanded state at 420. The compound works its way between conductors asit expands to ensure that none are touching each other when the compoundis fully expanded. An explosion proof seal is formed. The term“explosion proof” refers to normally encountered explosive environments.It is not meant to cover environments not normally anticipated inenvironments where such fittings are utilized.

1. A fitting for connecting conduit, the fitting comprising: a pluralityof electrical conductors running through the fitting, wherein thefitting includes threaded openings such that each threaded opening isadapted to receive a threaded conduit that includes the plurality ofelectrical conductors; and a sealing compound that has been expandedwithin the fitting to separate the electrical conductors from each otherand sides of the fitting.
 2. The fitting of claim 1 wherein the fittingand the sealing compound provide an explosion proof seal.
 3. The fittingof claim 1 wherein the fitting includes a hub that is between one-halfinch and six inches.
 4. The fitting of claim 1 further comprising a plugthat is secured within an additional opening in the fitting such thatthe plug is inserted into the opening after the sealing compound isadded to the fitting through the opening, wherein the threaded openingsare located at opposing ends of the fitting and the additional openingis located between the threaded openings.
 5. fitting of claim 1 whereinthe sealing compound is a two part mixture that starts to expand oncethe two parts of the two part mixture are mixed together.
 6. A method offilling a fitting having electrical conductors running through thefitting, the method comprising: adding a sealing compound to thefitting; and allowing the sealing compound to expand in the fitting suchthat the electrical conductors are separated and the fitting provides anexplosion proof seal when the fitting is attached to conduits that housethe electrical conductors.
 7. The method of claim 6 wherein allowing thesealing compound to expand in the fitting such that the electricalconductors are separated includes allowing the sealing compound toexpand to approximately four times in size.
 8. The method of claim 6wherein allowing the sealing compound to expand in the fitting includesallowing the sealing compound to expand in the fitting such that thesealing compound expands to fill a sealing chamber inside the fitting.9. The method of claim 6 further comprising mixing the sealing compoundbefore adding the sealing compound to the fitting.
 10. The method ofclaim 9 wherein mixing the sealing compound includes mixing the sealingcompound at a temperature approximately between 4° C. and 29° C.
 11. Afitting for connecting conduit, the fitting comprising: a plurality ofconductors running through the fitting; a sealing compound that has beenexpanded within the fitting to separate the conductors from each otherand sides of the fitting; and a first plug that is secured within afirst opening in the fitting such that the first plug is inserted intothe first opening after the sealing compound is added to the fittingthrough the first opening.
 12. The fitting of claim 11 wherein the firstplug is threaded into the first opening.
 13. The fitting of claim 11wherein the fitting and the sealing compound provide an explosion proofseal.
 14. The fitting of claim 11 wherein the conductors are electricalconductors.
 15. The fitting of claim 11 wherein the fitting includes ahub that is between one-half inch and six inches.
 16. The fitting ofclaim 11 further comprising a second plug that is secured within asecond opening in the fitting.
 17. The fitting of claim 11 wherein thefitting includes threaded openings such that each threaded opening isadapted to receive a threaded conduit that includes the plurality ofconductors.
 18. The fitting of claim 11 wherein the sealing compound isa two part mixture that starts to expand once the two parts of the twopart mixture are mixed together.